The slow-twitch muscle fibers got bigger no matter what kind of workout or drink the men used—whether they lifted slowly up or down, or drank protein or sugar water.
Scientific Claim
Type I muscle fiber growth occurs independently of resistance training mode or protein supplementation, increasing by 12–22% across all groups after 12 weeks, suggesting these fibers are less responsive to extrinsic modulators like protein or contraction type.
Original Statement
“Type I fiber CSA increased similarly with Conc training (22 ± 6% and 12 ± 5%) as well as Ecc training (14 ± 6% and 16 ± 8%) (P < 0.001) in the Whey and Placebo group, respectively.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The claim uses associative language and accurately reflects the data showing no differential effect across groups. No causal language is used, and the design supports this correlational interpretation.
Evidence from Studies
Supporting (0)
Contradicting (1)
Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth.
Even though all groups’ slow-twitch muscle fibers got bigger, the study found that how you exercise (pushing up vs. lowering down) changed important cellular processes that help muscles grow, meaning the type of exercise does matter—even for these fibers.